Risks from copper present in edible mushrooms naturally growing in Leicestershire, England

Objectives: Despite the potential risks from urban contamination, the popularity of home grown urban food products is increasing. We aimed to assess the risks from copper (Cu) present in wild edible mushrooms collected in Leicester city and a rural location (UK).

Methods: Twenty-two Agaricus bitorquis samples were collected from an open green area close to St Augustine Road, in the inner city; four Marasmius oreades samples were collected from the northeast of the city; and eight Coprinus atramentarius samples were collected from Bradgate Park, Charnwood Forest. Species identification was confirmed by DNA barcoding. Cu was detected in all the mushrooms collected by ICP-MS [LoD=2.224 mg/kg dry weight (dw)].

Results: Levels of Cu arguably showed species dependence across the species that we sampled, although further studies will be needed to dismiss the potential confounding effect of the geographical location (p-value<0.001; all data presented as median and ranges, in mg/kg dw): A. bitorquis [114.908 (101.1-186.2)] > C. atramentarius [68.202 (29.040-106.660)] > M. oreades [65.810 (49.0-83.320)]. The very high levels of Cu found in A. bitorquis could be explained by the high-traffic density of the adjacent road, recommending the performance of a risk assessment study for traffic-related metals. Thus, the bioconcentration factor value calculated as an average (1.845) suggests that Cu was bioaccumulated in Leicester’s native mushrooms. Cu also exhibited significant concentrations in the A. bitorquis caps compared to the stipes (114.908 vs. 93.303; p-value<0.001), which is the portion that is more likely to be consumed. The content of Cu was much higher than that reported in wild edible mushrooms from Greece (32.6 mg/kg dw) and also exceeded the maximum limit of Cu of 40 mg/kg established by FAO/WHO/CODEX standards. However, all the toxic risk quotients calculated following US EPA protocols were below the following units: 3.29E-02 (A. bitorquis), 1.73E-02 (C. atramentarius), and 1.74E-02 (M. oreades).

Conclusions: The consumption of wild edible mushroom species in Leicestershire should be discouraged.